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The magnetic circuit shown in Fig. P4.1 has dimension givens in millimeters and

ID: 2083815 • Letter: T

Question

The magnetic circuit shown in Fig. P4.1 has dimension givens in millimeters and with 500 turn coil. The Fig. P4.2 shows the magnetizing characteristics of the magnetic material. The magnetic circuit has a uniform thickness (depth) of 20 mm and the flux density in the air gap is 1.0 T (Wb/m^2). Determine the length of air-gap (ab) Calculate the cross-section area of the air gap. Calculate the flux in the air-gap Calculate the magnetic density of the air-gap. Calculate the magnetic intensity in the air-gap Calculate the reluctance of the air-gap Calculate the ampere-tums in the air-gap Complete the table Table P4.1 Draw the equivalent magnetic circuit Calculate the total ampere-tums in the coil. Determine the current required in the 500-tum coil.

Explanation / Answer

Solution:

(a) i. The distance ab= 150-80-60 = 10 mm

ii. cross section area of the air-gap = 10 x 6 =60 mm2

iii. Flux in air-gap = flux density x area = 1.0 x 60 x 10-6 = 6 x 10-6 Wb

iv. Magnetic density (flux) = 1.0 Wb/ m2  

v. Magnetic intensity = 833.3 A/m ...... from the graph corresponding to Flux density of 1.0 T

vi. Reluctance = R = MMF(Magnetomotive Force ) / (MF) Magnetic flux

= (833.3 x 6 x 10-3) / ( 6 x 10-6 ) Wb = 833.3 x 103 A/Wb

vii. Ampere turns =  MMF(Magnetomotive Force ) =  (833.3 x 6 x 10-3) = 5 A